Cranes are lifting machines used on construction sites to hoist heavy things in heights. We can find tower cranes, mobile cranes, crawler cranes and auxiliary canes. Some cranes are especially conceived to meet specific needs: forestry cranes or harbor cranes.

A tower crane is a fixed crane weighted at its base, often used on skyscraper building sites. It may be a self-erecting tower crane, also called self-assembling crane, jack-up crane or kangaroo crane. The self-erecting tower crane is extended quickly and automatically by the operator either from the cab or at ground level with a controller. The self-assembling crane assembly is made thanks to the successive adding of elements from the base with a hydraulic cylinder system. They are taller than self-erecting tower cranes and must be fixed to a building. A tower crane is mainly composed of a mast, a lifting system, a counterweight and a jib to which may be fixed a grapple, a cable or a hook.

Mobile cranes are truck-mounted cranes. Even if they are easy to move, they still benefit from high lifting capacities. Their jib may be telescopic. Crawler cranes are heavier and then steadier than mobile crane. Therefore, they are able to move great loads. Auxiliary cranes are smaller and can be fixer to a truck or a tractor. They payload is then reduced.

Cranes are used since Ancient Greece and were traditionally made of wood. They became metallic at the end of 19th century. Different makers (Liebherr, Potain, Grove) have developed wide ranges of models since then.